A leakage detection protection circuit disclosed by a Chinese Patent Application No. 201310452956.0 includes a power input end, a power user end, a power output end, a reset button, a main circuit switch linked with the reset button, twin induction coils for detecting leakage current and low resistance failure, a trip coil allowing the reset button to drive the main circuit switch to be closed or open/disconnected by driving a built-in iron core under the action of a magnetic field in collaboration with a mechanical structure, a silicon controlled rectifier for providing a path for analog leakage current, a control chip which may determine whether the silicon controlled rectifier is on or off according to a detection result of the twin induction coils, and a timed self-checking circuit. The leakage detection protection circuit is provided with a normally-open switch K1 linked with the reset button. The normally-open switch K1 is driven to be closed when the reset button is pressed down after the initial installation. The analog leakage circuit produces a current through resistor R7, leading to short circuiting the power input end. When the control chip detects the leakage current via the twin induction coils, the silicon controlled rectifier is driven to be turned on. After the trip coil is energized, the iron core moves and drives a latch in a leakage protection outlet to move. After being positioned by a locking piece lockhole hook, a guide pillar of the reset button rises to drive the main circuit switch to be closed. When the circuit is operating properly, in case of a reversed wire connection (e.g., wherein main power supply is mistakenly connected the power output end), a normally-closed switch connecting the power output end and the power user end is disconnected via a mechanism such as the control chip or the silicon controlled rectifier. Such reversed wire connection protection is unavailable when the mechanism such as the control chip or the silicon controlled rectifier is damaged.
Chinese Patent Application No. 201410112524.X discloses a leakage detection protection circuit having timed self-checking and reversed wire connection protection function. To implement the reversed wire connection protection and ensure that exactly two of the power input end, the power output end (e.g., load), and the power user end (e.g., electrical outlet) are electrically connected at any given time (e.g., there are always two groups of mutually isolated conductors), the circuit structure of the leakage detection protection circuit is further provided with normally-open switches (e.g., K3B-1 and KR3B-2) in addition to the main circuit switch. Therefore, such a leakage detection protection circuit is complex in structure, and is difficult, labor-intensive, and time-consuming to accurately assemble.
The disclosure of Chinese Patent Application No. 201410367800.7 offers some solutions to the above-described problems. However, some deficiencies still exist: For example, two trip coils are included, thus such solutions are relatively complex in structure and relatively inconvenient for processing and assembling.
The disclosure of Chinese Patent Application No. 201410667103.3 provides a solution for above technical problems. However, its solution may have several shortcomings: First, two ends of a dynamic contact lever of the main circuit switch have a dynamic contact point, and in the middle there is provided with a seesaw structure. Therefore, such configurations demand precision in processing, assembling, and action. An internal pressure test (continuously turned on/off for thousands of times) may cause poor contact among contact points, which could be a hidden danger. Second, beneath the seesaw dynamic contact lever, the seesaw dynamic contact lever is connected with a flexible lead. It is difficult to ensure reliable action of flexible lead and the precision of the seesaw dynamic contact lever. Third, a reversed wire connection circuit is not provided with a current-limiting circuit, and thus components (such as the trip coil) may likely be damaged due to temperature rise if the main circuit switch cannot timely trip during reversed wire connection. Fourth, after the reset button is pressed down, the dynamic contact lever of a normally-closed reversed wire connection path switch K5 is disconnected under pressure, and is closed after the pressed down is released. Thus, such a configuration demands precision in action, making it difficult to process and assemble.